Generally, to open a conventional container, a portion of top portion thereof should be cut-away using an additional tool such as scissors. Therefore, it is a troublesome for a user to have to use such a tool whenever the user intends to open the container
To solve the above problems, containers each having an easy opening structure have been provided for a square/hexahedron container. However, such an easy opening structure cannot be applied to a tetrahedron or pentahedron container due to its structural limitation.